C Alphabet Triangle Pattern (Reverse Start)

Beginner
6 min read
Updated: Sep 2026
3 programs
Live preview
Alphabet triangle pattern E, DE, CDE, BCDE, ABCDE in C programming
Definition

What Is This Pattern?

A reverse-start alphabet triangle keeps the right edge fixed at a top letter while each row begins one letter earlier — letters along the row still run forward.

Remember
Rule: for start i from top down to A,
      print letters i..top, then newline

E
DE
CDE
BCDE
ABCDE     ← top = 'E'

Unlike Program 1 (always starts at A) and Program 2 (prints letters backward along the row), this pattern only moves the first letter; every row still ends at top.

Approach

How to Solve It

Descend the start letter on the outer loop; ascend from that start to top on the inner loop.

MethodIdeaBest for
Compact lettersprintf("%c", j) with no spacesLearning, interviews, exams
Spaced lettersprintf("%c ", j) (letter + space)Readable columns in demos

Pseudocode

Pseudocode
top = 'E'   // or 'A' + rows - 1
for i from top down to 'A':
    for j from i to top:
        print j
    print newline

Cheat sheet

GoalPattern
Pick the start letterfor (i = top; i >= 'A'; i--)
Print forward to topfor (j = i; j <= top; j++)
Print a letterprintf("%c", j);
End the rowprintf("\n");
Top from row counttop = (char)('A' + rows - 1);

Printing Letters vs Starting a New Line

APIEffectUse for
printf("%c", j)One letter; stays on the lineEach letter in the row
printf("\n")Ends the current lineAfter the letter loop
Try it

Live Preview

Change the row count (top = A + n - 1) and the triangle updates instantly — capped at 8 for readability.

Whole numbers from 1 to 8. With n = 5, top is E and you get the classic sample.

Live result 5 rows · 15 letters
E
DE
CDE
BCDE
ABCDE
Trace

Worked Walkthrough — top = 'C'

Three rows (n = 3) so each start letter is easy to check by hand.

Start iInner j valuesPrinted row
'C'CC
'B'B, CBC
'A'A, B, CABC

Every row ends at 'C'; only the first letter moves earlier as i decreases.

Code

C Programs

Three complete programs: fixed top letter, scanf row count, and a spaced-letter variant. Use View Output to reveal sample results.

Example 1 — Fixed top at 'E'

Hard-coded top — outer loop picks the start; inner loop prints forward to 'E'.

C
#include <stdio.h>

int main(void)
{
    char i, j;

    for (i = 'E'; i >= 'A'; i--)
    {
        for (j = i; j <= 'E'; j++)
            printf("%c", j);
        printf("\n");
    }

    return 0;
}

How It Works

1. Outer loop moves the start. i runs from 'E' down to 'A' — one row per start letter.

2. Inner loop runs forward. From i up to 'E', so when i = 'C' you get CDE.

3. Right edge stays fixed. Every row ends at 'E'; only the left edge grows leftward.

4. Break the line. printf("\n") after the letter loop starts the next earlier start.

Example 2 — User Input Version

Read the row count, set top = 'A' + rows - 1, then use the same loops.

C
#include <stdio.h>

int main(void)
{
    int rows;
    char top, i, j;

    printf("Enter the number of rows: ");
    scanf("%d", &rows);

    top = (char)('A' + rows - 1);

    for (i = top; i >= 'A'; i--)
    {
        for (j = i; j <= top; j++)
            printf("%c", j);
        printf("\n");
    }

    return 0;
}

How It Works

1. Prompt and read. scanf("%d", &rows) sets how many letters appear on the last row.

2. Compute the top letter. For rows = 4, top becomes 'D'.

3. Same triangle core. Only top changes; start still descends and letters still run forward.

4. Safer input tip. Reject bad or oversized values:

Safer input
if (scanf("%d", &rows) != 1 || rows < 1 || rows > 26)
{
    printf("Enter a whole number from 1 to 26.\n");
    return 1;
}

Example 3 — Spaced letters

Same shape with printf("%c ", j) so letters sit in readable columns.

C
#include <stdio.h>

int main(void)
{
    char i, j;
    char top = 'E';

    for (i = top; i >= 'A'; i--)
    {
        for (j = i; j <= top; j++)
            printf("%c ", j);
        printf("\n");
    }

    return 0;
}

How It Works

1. Same loops. Start still descends; letters still run forward to top.

2. Only the print format changes. "%c " adds a trailing space after each letter.

3. Learn compact first. Use Examples 1–2 when matching exam samples; add spaces when you want clearer columns.

Edge Cases & Pitfalls

Check these before calling the solution done.

Wrong direction

Descending inner loop

If j counts down from top, you get Program 2’s pattern — not this one. Keep j++ from i to top.

Wrong start

Always starting at A

Starting every row at 'A' rebuilds Program 1. The outer start must be i, not a fixed 'A'.

\n early

Broken rows

Call printf("\n") only after the letter loop finishes.

rows = 1

Single A

Output is just A — one start, one letter.

rows > 26

Past Z

Clamp to 26 for A–Z demos, or define a clear wrap/error policy.

scanf

Check the return value

If scanf fails, rows is uninitialized — always test == 1.

Analysis

Time and Space Complexity

ProgramTimeExtra space
Compact (Examples 1–2)O(n²)O(1)
Spaced (Example 3)O(n²)O(1)

For n rows the letter count is 1 + 2 + … + n = n(n+1)/2 — quadratic in n.

Remember

Key Takeaways

  • Rule: start at i, print forward to a fixed top.
  • Outer descends: i from top down to 'A'.
  • Break the row: call printf("\n") only after the letter loop.
  • Complexity: O(n²) time; O(1) extra space.

One line: for each start i from top down to A, print i..top, then printf("\n").

Frequently Asked Questions

The outer loop moves the starting letter from E down to A. The inner loop always prints forward from that start letter up to E (or top), so the last character remains E on every row.
Program 2 prints letters descending along the row (E, ED, EDC). This program prints forward along the row (E, DE, CDE) while only the row’s first letter moves backward.
Program 1 always starts at A and grows the end letter (A, AB, ABC). This pattern grows the start letter backward while keeping the right edge fixed at top.
printf("%c", j) prints a letter and stays on the same line. printf("\n") ends the current line after the letter loop finishes.
Yes. Read rows with scanf and set top = (char)('A' + rows - 1). Then loop i from top down to 'A' and print j from i up to top.
O(n²) for n rows, because the total printed letters are 1+2+…+n = n(n+1)/2.
Check scanf("%d", &rows) == 1, require n ≥ 1, and cap at 26 so the top letter stays within A–Z.
Because the inner loop always stops at top (E in the fixed example), so the last printed character is always that same letter.

Did you know?

This triangle changes only the starting letter of each row (E, D, C, …), while letters along the row still increase forward. In the 5-row example, every row ends at E, producing E, DE, CDE, BCDE, ABCDE.

Next: Reverse Order Triangle

Print alphabet rows that shrink with reverse letter order.

Program 4 tutorial →

About the author

Mari Selvan M P
Mari Selvan M P 🔗

Developer, cloud engineer, and technical writer

  • Experience 12 years building web and cloud systems
  • Focus Full Stack Development, AWS, and Developer Education

I write practical tutorials so students and working developers can learn by doing—from databases and APIs to deployment on AWS.

AWS Certified Developer – Associate (Credly)

12 people found this page helpful

C Alphabet Pattern 2 — Reverse Triangle C Alphabet Pattern 4 — Reverse Order Triangle